Process for the recovery of tungsten from its ores



United States Patent Office 3,271,104 Patented Sept. 6, 1966 3,271,104PROCESS FOR THE RECOVERY OF TUNGSTEN FROM ITS ORES Joseph P. Surls, Jr.,Walnut Creek, Califi, assignor to The Dow Chemical Company, Midland,Mich., a corporation of Delaware No Drawing. Filed Feb. 7, 1963, Ser.No. 256,842 6 Claims. (CI. 23-19) This invention relates to a processfor recovering tungsten values from tungsten bearing materials. Moreparticularly it is concerned with a novel method for recovering highquality tungsten values in high yields from tungsten ores such aswolframite, ferberite, hubernite, scheelite, scheelite-powellite and thelike.

Tungsten containing ores usually processed in this country and elsewherein the world are scheelite (CaWO scheelite-powellite (CaWO -FeWO andWolframite (Mn, Fe)WO scheelite being the most common. The scheelite andscheelite-powellite ore deposits generally contain as an impuritymolybdenum, primarily as CaMoO and molybdenum sulfide. The molybdenumsulfide readily is removed and separated, but the calcium molybdate,which is in isomorphic mixture with the scheelite, is not separable bytraditional grinding and milling techniques. conventionally, to recoverand separate these constituents, i.e. molybdenum and tungsten, toprovide high purity tungsten products substantially free from molybdenumthese ores or .ore concentrates are subjected to lengthy and complicatedchemical dissolution methods, usually at moderately high temperaturesand atmospheric or elevated pressures. The tungsten is recovered asprecipitated crude tungsten oxide containing considerable quantities ofimpurities. Ordinarily the crude oxide is redissolved in an alkalinemedium and the tungsten reprecipitated from solution. This dissolutionand precipitation ordinarily is carried out at least two times afterwhich the resulting tungsten oxide is treated with strong ammonia toconvert it to the paratungstate. This product is separated from thereaction solution, dried and ignited thereby to provide a relativelyhigh purity tungsten oxide.

Kasey (U.S. 2,801,152) alleges an improvement over the conventional andcostly multi-step traditional art processes by treating finely dividedtungsten ores at elevated temperatures with concentrated aqueoushydrochloric acid containing an HCl concentration of from 35 to 37.8weight percent. At least 20 cubic centimeters of the acid are used foreach gram of tungsten, expressed as tungstic oxide (W in the ore. Thistreatment allegedly dissolves both the tungsten and molybdenum values inthe ores. The solution containing these values is separated from theresidual insoluble material. The dissolved tungsten values subsequentlyare precipitated as the oxide while maintaining the molybdenum values insolution. Although this process is a more economical way than theconventional art processes for recovering tungsten in high purity fromits ores, the solubility of tungsten in the concentrated aqueoushydrochloric acid employed in the process is rather low. Therefore,large amounts of the hydrochloric acid acidulating agent, withcorrespondingly large storage vesels and handling and tranfer equipment,must be employed.

Now, unexpectedly, the present invention provides a tungsten oredissolution process whereby a marked increase in dissolved tungstenvalues per unit of dissolving agent is achieved over the prior artprocesses.

It is a principal object of the present invention to provide a novel,low temperature ore dissolution process whereby high purity tungstenvalues are recovered directly and in good yield.

It is another object of the present invention to provide a novel processfor recovering tungsten from its ores wherein process plant size andreagent recycle requirements are markedly reduced over that required byknown art processes.

In accordance with the process of the present invention, a tungstenbearing source material, usually a tungsten ore or ore concentrate suchas scheelite or scheelite ore concentrate, is contacted at atmosphericor superatmospheric pressures and a temperature of from about 40 toabout C., preferably from about 50 to about 60 C., for a period of fromabout 0.25 to about 4 hours or more and preferably from about 0.5 toabout 2 hours, with a concentrated alcoholic hydrogen halide solutionthereby to dissolve the tungsten values contained in the sourcematerial. The resulting solution containing the dissolved tungstenvalues is separated from the insoluble residue of gangue and other solidimpurity materials. The solution is heated above 70 C., ordinarily toabout reflux, and/ or otherwise reduced in hydrogen halide content bydilution, neutralization and the like whereupon high quality tungstenvalues precipitate directly therein.

The actual separation of the alcoholic hydrogen halide solutioncontaining dissolved tungsten values from the residual solids readily iscarried out by filtration, centrifugation, settling and decantation, orother traditional solid-liquid separation techniques as is apparent toone skilled in the art.

Conveniently, the tungsten values are precipitated by boiling theseparated alcoholic hydrogen halide solution in order to reduce thehydrogen halide content. Preferably the hydrogen halide content of thesolution is reduced by distilling ofi a portion of the solution. Thedistillate is recovered and can be used directly as make-up reagent forsubsequent acidulation of additional tungsten source material. Theresulting precipitated tungsten values readily are separated from theresidual alcoholic hydrogen halide solution. An advantage of the presentprocess is that with glass or glass-lined reactors the solid productreadily is removed from the reactor. In an acidulation process employingconcentrated aqueous hydrochloric acid acidulating agent, the resultingprecipitated tungsten values adhere tenaciously to glass reactor wallsand are difiicult to remove from the reactor.

The separated tungstic acid can be washed substantially free ofimpurities. Concentrated aqueous hydrochloric acid (e.g. from about 6 toabout 12 M HCl) is used as an initial wash to assure removal ofundesirable elements or compounds which may have been absorbed, absorbedor otherwise associated with the precipitated tungsten product.Preferably there is added to this wash material about 0.05 Weightpercent HNO This latter component assures development of the typicalbright yellow color in tungstic oxide produced by calcining theprecipitated tungstic acidproduct. This Wash is effective in removingthe bulk of the impurities. Dilute acid, e.g. 0.25% HCl, or salts, e.g.1% NH Cl, or water can be used for subsequent washes of the product, ifdesired. Although water alone is satisfactory in these final washes,salt or weak acid solutions are preferred as washing with water alonesometimes converts the precipitated crystalline tungstic acid into ahard to handle colloidal form. The resulting tungstic acid (H WO productcan be dried and used directly, converted by ignition to thecorresponding oxide (WO or otherwise converted into useful tungstencompounds or materials.

In the present novel process, ordinarily the ore, ore concentrate orother tungsten source material is finely divided, i.e. ground or milledto pass a No. 200 US. Standard Sieve before acidulating with thealcoholic hyhandling and storage equipment and the like for use in theprocess are fabricated from materials which are substantiallynon-reactive with the reactants and products. Also, this processingequipment must have the requisite drogen halide solution. The largesurface area to weight 5 structural strength for operation at thespecified reaction ratio present in the finely ground material assures aready conditions. winning of the tungsten values in a shorter reactiontime. The following examples will serve further to illustrate However,this pretreatment is not critical or limiting as the present invention,but are not meant to limit it thereto. larger ore particles acidulatesatisfactorily. Example grams of a soheelite 0T6 C H- The alcoholcomponent, i.e. solvent, of the acidulating r t assaying about 70% W0was reacted at about agent is selected from the group consisting ofaliphatic atmospheric pressure and about 60 C. for one hour withmonohydric alcohols containing from 1 to 3 carbon about 100 millilitersaqueous ethanolic hydrogen chloride atoms. The hydrogen halide, solute,is a member sesolution. The HC1/W0 weight ratio in the original relectedfrom the group consisting of hydrogen chloride action mix was about 3.4.The acidulating reagent was and hydrogen bromide. Preferably anethanolic hydro- 15 P p y miXhlg 50 milliliters of an moliu' q genchloride solution containing from about 30 to about ous hydrogenchloride solution and 50 milliliters of a 33 weight percent HCl is usedas acidulating agent. molar ethuhohc hydrogen Chloride Solutioh- Thealcoholic hydrogen halide solution is employed resulting aqueous ethanolVolume miXtufo] S0111- either as a substantially anhydrous alcoholsolution or an (ion Containing about 32 Weight Percent Followaqueous alhol l ti h i up t b t 70 ing the reaction period, the resulting solutionwas filtered nt of th l ohol ha be replaced ith t to separate the acidinsolubles therefrom. The solid resi- Ordinarily with a substantiallyanhydrous alcohol reduo Was dried and g The dry Weight Was about agent,the alcohol is saturated with hydrogen halide. A This residue P analysisWas found to saturated solution of hydrogen chloride dissolved in antaihabout 0-075 gram 3 indicating Solubihlatioh of hydrous ethanol at about50 C. contains about 8.5 moles about 992% of the tungsten Values intothe ethuhoho HCl per liter; on a weight basis this solution containshydrogen chloride H about 31.9 weight percent HCl. At about 60 C. sub-The resulnng 501mm was heated at stantially anhydrous ethanol saturatedwith HCl provides Perature for about twenty mmutes dunng W h i about a7.6 molar solution; this solution, on a weight It was concentrated toabout 70 percent ofclts ongmal basis has a Hcl content of about 299percent volume and the temperature rose to about 90 C. the

lutlon became concentrated a dense ellow reci 1tate A ueous alcoholic hdro en chloride solution within so y P p q y s of tungstic acid formed.This sol1d product was separated the alcohol-Water composltion rangedescribed hereinbeby filtration and Washed. The dried HzWQ4 productfore, also provide unexpectedly high, effective tungsten Weighed9 182grams. hssolutloh markedly Improved ovol that obtalhod from Theresulting filtrate was distilled to recover the ethause of aqueousconcentrated hydrochloric acid. In fact, 1 d HCL aqueous ethanolhydrogen chloride solutions wherein Example 2.-A tungstic acid productobtained by folfrom about 25 to about 60 volume percent of the ethanollowing the same procedural steps and reaction conditions is replacedwith water, accommodates greater amounts of as described in Example 1was washed first with concendissolved tungsten values than thesubstantially anhydrous trated hydrochloric acid containing about 0.05weight perethanolic hydrogen chloride acidulating agent itself. cent HNOfollowed by dilute (0.25%) aqueous hydro- Ordinarily, aqueous alcoholichydrogen chloride solutions chloric acid, dried and converted totungstic oxide by as are employed in the present process contain ahydrogen ignition. The product was analyzed by emission spectrochlorideconcentration of about 33 weight percent hydrographic techniques. Theanalytical results are presented gen chloride. in Table I. The analysisof a known high purity tungstic Satisfactory high recoveries of tungstenvalues from acid product prepared with concentrated aqueoushydrotungsten source materials are obtained in the present procchloricacid in accordance with the teaching of the Kasey ess by use ofsufiicient alcoholic hydrogen halide solution patent, US. 2,801,152,also is included in Table I for such that the ratio of hydrogen halidein the acidulating comparative purposes,

TABLE I Impurities, p.p.m. W03 Sample Al B B0 Ca. Cu Fe Mg Mn M0 Na SiTi V Pdt.from Alcoholic HC1. 10 5 10 1 10 10 10 300 1n0 Pdt.from Aq.1101 (Kasey) 10 4 10 2 10 10 10 270 400 100 *N one detected.

solution to tungsten values in the ore, expressed as the Example 3.Aseries of runs was made to determine weight ratio f HC] gquivalent totungstic id 0 the effectiveness of various hydrogen chloride leachsoluis at least about 3. Alcoholic solution in excess of the tlohs indissolving tungsten o Sohoehto I required amount can be used, ifdesired. Use of larger For thls expenment a Welghed amount o schoohtoquantities of the solution can aid in the handling of the Oreconcentrate t 70% W0 was mixed with a reaction mixture, promote materialtransfer and the like known Volume of sohmon a f lf type bottle? theoperations. Any unreacted acid, in excess of that re- 70 Potfle wascapped and retultmg mixture 2 placed 1 tion of the Ore is not lost butcan be 1n a thermostated bath maintained at about 60 C. Folquu'ed foracid a H lowing an extended contact period, about 28 hours, to recycledfor subsequent treatment of additional tungsten assure that the Systemwas at equilibrium, the solution Source materialwas analyzed fortungsten content.

The Present Process can be carried in batch yp Table II which followspresents the results of this continuous or cyclic operations. Reactors,material 7 5 study.

TAB LE II H01 Solution, In]. Solution Analysis, W03 Scheelite ore RunN0. concentrate, W03 HCl, wt. gm. H01, gmJgm.

gm. Ethanolic 2 Aqueous 3 Gm./ml. Percent dissolved 1 Ore concentrateabout 70% by weight W0 2 7.50 M H01 in substantially anhydrous ethanol;about 29.3% E01 by weight.

3 11.1 M H01 in water; about 345% H01 by weight. 0

4 Mixed solution contains about 32.4% H01 by weight.

These equilibrium studies clearly show the improved solubilities oftungsten in an alcoholic hydrogen chloride solution as compared to thesolubility of this same metal in a concentrated aqueous hydrochloricacid solution even though the HCl content of the aqueous solution Wasconsiderably greater than in the alcoholic HCl solution.

Example 4.A number of tests were carried out evaluating the solubilityof tungsten in a number of alcoholic hydrogen chloride solutions.

For this run, four grams of scheelite ore concentrate (70% W0 wereweighed into a bottle, and a total of 20 milliliters of hydrogenchloride solution was added. The bottle then was sealed and rotated in athermostated bath at 60 C. for about four hours. The results of thesetests are presented in Table III which follows:

TABLE III ontrol Alcoholic H01 solution (wt. percent H01) Tungstensolubility (tungsten oxide/liter solution) Run No.

Substantially anhydrous.

In a manner similar to that described for the foregoing exampleshydrogen bromide can be substituted for hydrogen chloride in thealcoholic acidulating agent employed in the novel process of the presentinvention.

I claim:

1. A process for recovering high purity tungsten values from tungstensource materials which comprises:

(a) reacting a tungsten bearing source material with a concentratedalcoholic hydrogen halide solution acidulating agent at a temperature offrom about 40 to about 70 C. for a period of from about 0.25 to about 4hours employing an amount of said acidulating agent such that theoriginal hydroger halide/tungsten weight ratio of the reaction mixexpressed as equivalent HCl/WO is at least 3 thereby to dissolvesubstantially all of the tungsten values present in said tungstencontaining source material, the alcohol component of said acidulatingagent being a member selected from the group consisting of aliphaticmonohydric alcohols containing from 1 to 3 carbon atoms, and thehydrogen halide being a member selected from the group consisting of HCland HBr, said concentrated alcoholic hydrogen halide solution beingsaturated with said hydrogen halide based on said alcohol componentbeing substantially anhydrous, and said alcoholic hydrogen halidesolution being further characterized as having from 0 to about 70 volumepercent of said alcohol replaced with water,

(b) separating the resulting solution containing substantially all ofthe tungsten values present in said tungsten bearing source materialfrom any undissolved solid residue,

(c) treating said solution thereby to precipitate said tungsten valuestherein by reducing the hydrogen halide concentration therein,

(d) separating said precipitated tungsten values from the residualsolution and Washing said precipitated tungsten values; and,

(e) recovering said precipitated tungsten values as a high purityproduct.

2. A process for recovering tungsten values in high purity from atungsten ore material which comprises:

(a) reacting a tungsten bearing ore material with a concentratedalcoholic hydrogen chloride solution acidulating agent at a temperatureof from about 50 to about 60 C. for a period of from about 0.5 to about2 hours employing an amount of said acidulating agent such that theoriginal HCl/tungsten ratio of the reaction mixture, expressed as-HCl/WO on a weight basis is at least 3 thereby to dissolvesubstantially all of the tungsten values present in said tungstenbearing ore material, said alcoholic hydrogen chloride acidulating agenthaving a HCl content ranging from about 30 to about 33 weight percentand the alcohol component of said acidulating agent being a memberselected from the group consisting of methanol, ethanol, 1-propanol and2-propanol, said alcoholic hydrogen chloride solution being furtherecharacterized as having from 0 to about 70 volume percent of saidalcohol replaced with water,

(b) separating the resulting alcoholic hydrogen chloride solutioncontaining substantially all of the tungsten values present in saidtungsten bearing ore material from any undissolved solid residue,

(0) heating said solution to reflux thereby to precipitate said tungstenvalues therein as a high purity crystalline tungstic acid,

((1) recovering said precipitated tungstic acid from said solution, and

(e) washing said precipitated tungsten acid substantially free ofimpurities.

3. A process for recovering high purity tungsten values in high yieldfrom a scheelite ore which comprises.

(a) reacting a member selected from the group consisting of scheeliteores and scheelite ore concentrates with an ethanolic hydrogen chloridesolution acidulating agent at a temperature of from about 50 to about 60C. for a period of from about 0.5 to about 2 hours employing an amountof said acidulating agent such that the original HCl/tungsten ratio ofthe reaction mixture, expressed as HCl/WO on a weight basis is at leastabout 3.4 thereby to dissolve substantially all of the tungsten valuespresent in said scheelite, said ethanolic hydrogen chloride acidulatingagent having an HCl content ranging from about 30 to about 33.5 weightpercent, said ethanolic hydrogen chloride acidulating agent beingfurther characterized as having from 0 to about 70 volume percent of theethanol replaced by water,

( b) separating the resulting ethanolic hydrogen chloride solutioncontaining substantially all of the tungsten values originally presentin said scheelite from the non-soluble residue,

7 (c) concentrating said solution to about 70 volume percent of itsoriginal volume thereby to precipitate said tungsten values therein as acrystalline tungstic acid,

((1) recovering said precipitated tungstic acid from said solution, and

(e) washing said precipitated tungsten acid with concentratedhydrochloric acid.

4. The process as defined in claim 3 and including the steps of Washingthe recovered precipitated tungstic acid with concentrated aqueoushydrochloric acid containing about 0.05 weight percent HNO (a) dryingthe washed product, and,

(b) igniting the dried, washed tungstic acid thereby to provide a brightyellow, high purity tungstic oxide.

5. The process as defined in claim 3 wherein the ethanol solvent of saidacidulating agent is a member selected from the group consisting ofsubstantially anhydrous ethanol and aqueous ethanol solutions, saidaqueous ethanol solution being at least about volume percent ethanol.

6. The process as defined in claim 3 wherein the ethanol solvent of saidacidulating agent is an aqueous ethanol solution containing from about30 to about 75 volume percent ethanol and from about to about 25 percentwater.

References Cited by the Examiner UNITED STATES PATENTS 984,143 2/1911Lederer 23-21 2,366,250 1/1945 Foulke et al. 23-140 2,801,152 7/1957Kasey 2319 3,079,226 2/1963 Newkirk 23l9 3,193,347 7/1965 Forward et a123-140 OSCAR R. VERTIZ, Primary Examiner.

BENJAMIN HENKIN, MILTON WIESSMAN,

Examiners. H. T. CARTER, Assistant Examiner.

1. A PROCESS FOR RECOVERING HIGH PURITY TUNGSTEN VALUES FROM TUNGSTENSOURCE MATERIALS WHICH COMPRISES: (1) REACTING A TUNGSTEN BEARING SOURCEMATERIAL WITH A CONCENTRATED ALCOHOLIC HYDROGEN HALIDE SOLUTIONACIDULATING AGENT AT A TEMPERATURE OF FROM ABOUT 40 TO ABOUT 70*C. FOR APERIOD OF FROM ABOUT 0.25 TO ABOUT 4 HOURS EMPLOYING AN AMOUNT OF SAIDACIDULATING AGENT SUCH THAT THE ORIGINAL HYDROGEN HALIDE/TUNGSTEN WEIGHTRATIO OF THE REACTION MIX EXPRESSED AS EQUIVALENT HC/WO3, IS AT LEAST 3THEREBY TO DISSOVLE SUBSTANTIALLY ALL OF THE TUNGSTEN VALUES PRESENT INSAID TUNGSTEN CONTAINING SOURCE MATERIAL, THE ALCOHOL COMPONENT OF SAIDACIDULATING AGENT BEING A MEMBER SELECTED FROM THE GROUP CONSISTING OFALIPHATIC MONOHYDRIC ALCOHOLS CONTAINING FROM 1 TO 3 CARBON ATOMS, ANDTHE HYDROGEN HALIDE BEING A MEMBER SELECTED FROM THE GROUP CONSISTING OFHCL AND HBR, SAID CONCENTRATED ALCOHOLIC HYDROGEN HALIDE SOLUTION BEINGSATURATED WITH SAID HYDROGEN GALIDE BASED ON SAID ALCOHOL COMPONENTBEING SUBSTANTIALLY ANHYDROUS, AND SAID ALCOHOLIC HYDROGEN HALIDESOLUTION BEING FURTHER CHARACTERIZED AS HAVING FROM 0 TO ABOUT 70 VOLUMEPERCENT OF SAID ALCOHOL REPLACED WITH WATER, (B) SEPARATING THERESULTING SOLUTION CONTAINING SUBSTANTIALLY ALL OF THE TUNGSTEN VALUESPRESENT IN SAID TUNGSTEN BEARING SOURCE MATERIAL FROM ANY UNDISSOLVEDSOLID RESIDUE, (C) TREATING SAID SOLUTION THEREBY TO PRECIPITATE SAIDTUNGSTEN VALUES THEREIN BY REDUCING THE HYDROGEN HALIDE CONCENTRATIONTHEREIN, (D) SEPARATING SAID PRECIPITED TANGSTEN VALUES FROM THERESIDUAL SOLUTION AND WASHING SAID PRECIPITATED TUNGSTEN VALUES; AND,(C) RECOVERING SAID PRECIPITATED TUNGSTEN VALUES AS A HIGH PURITYPRODUCT.